Do Swift-based applications work on OS X 10.9/iOS 7 and lower?

Apple has announced that Swift apps will be backward compatible with iOS 7 and OS X Mavericks. The WWDC app is written in Swift.

I just tested it for you, Swift applications compile into standard binaries and can be run on OS X 10.9 and iOS 7.

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Simple Swift application used for testing:

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool {
    self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

    var controller = UIViewController()
    var view = UIView(frame: CGRectMake(0, 0, 320, 568))
    view.backgroundColor = UIColor.redColor()
    controller.view = view

    var label = UILabel(frame: CGRectMake(0, 0, 200, 21))
    label.center = CGPointMake(160, 284)
    label.textAlignment = NSTextAlignment.Center
    label.text = "I'am a test label"
    controller.view.addSubview(label)

    self.window!.rootViewController = controller
    self.window!.makeKeyAndVisible()
    return true
}

Swift code can be deployed to OS X 10.9 and iOS 7.0. It will usually crash at launch on older OS versions.